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RayBiotech Using Protein Array Tech to ID Biomarkers for Ovarian, Gastric, Liver Cancers

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RayBiotech is applying its protein array technology to internal protein biomarker discovery work.

The company is investigating potential panels for ovarian, gastric, and liver cancers with the ultimate aim of building clinical diagnostics that it could submit for US Food and Drug Administration clearance, CEO Ruo-Pan Huang told ProteoMonitor.

In a study published last year – also in PLOS One – by the company and its Sun Yat-sen University collaborators, in which they developed an antibody array for profiling the expression of insulin-like growth factor in patients with hepatocellular carcinoma. In that work, they identified the proteins IGF-2R and IGFBP-2 as potential markers for the disease.

Founded in 2001, the Norcross, Ga.-based company sells reagents and services aimed at immunoassay-based protein biomarker discovery. It offers services including array testing, biomarker discovery, and custom assay development, as well as hundreds of protein arrays and immunoassays for protein analysis.

Last month, the firm obtained ISO 13485:2003 certification for compliance in the manufacture of in vitro diagnostics kits provided to the research community. The certification applies to its multivariant antibody arrays, enzyme-linked immunosorbent assays, and membrane and glass format arrays and reagents.

According to Huang, the company is now looking to apply its immunoassay expertise to internal protein biomarker development efforts. It is taking several different approaches in this regard, he noted, in some cases working with its array technology to identify novel biomarkers; in other cases using the technology to test combinations of previously identified markers; and in some cases looking to create combinations of novel and previously identified markers.

Huang noted that while mass spectrometry is widely used for discovery-stage protein biomarker work, RayBiotech's array-based approach offers certain advantages – specifically sensitivity and ease of use.

"Most of [the firm's immunoassays] can detect [proteins] at the picogram-per-mL level," he said, compared to mass spec assays, which typically top out in the nanogram-per-mL range unless combined with upfront immunoenrichment steps.

Additionally, "using the array technique we have developed over the last decade is much easier [than running a mass spec,]" Huang said, noting that mass spec platforms typically require PhD-level researchers with several years of training.

The company is not alone, of course, in its immunoassay-based biomarker discovery efforts. Myriad RBM is the dominant player in this area, offering a number of Luminex-based panels for protein biomarker discovery, including its Human DiscoveryMAP 250+ product, which measures the levels of more than 250 proteins.

Olink Bioscience has also entered the biomarker discovery panel space with its proximity-ligation assay technology. In August, the company entered an agreement to offer its Proseek Multiplex protein assays on Fluidigm's BioMark HD real-time PCR platform, allowing researchers to measure in a single run the levels of up to 92 proteins in as many as 96 samples (PM 8/2/2013). Olink currently offers one discovery panel – its Proseek Multiplex Oncology I 96x96 Kit, which measures levels of 92 proteins linked to cancer. It plans to launch three additional panels – for inflammation, cardiovascular disease, and animal pharmacodynamics – this fall, at which point its panel offerings will total between 200 and 300 analytes.

Proteomics firm Somalogic offers protein biomarker discovery services using its aptamer-based Somamer technology. The company's SOMAscan platform currently features assays to more than 1,100 proteins.

According to Huang, RayBiotech's label-based array contains assays to roughly 1,000 different proteins. Its sandwich assay-based array contains assays to roughly 400 proteins.

As Huang acknowledged, a major issue for array-based biomarker discovery platforms is antibody cross-reactivity, which can create noise. The company's platform reduces this problem to an extent, he said, by depositing capture antibodies on the substrate surface, meaning that the antibodies aren't able to react with each other.

Cross-reactivity among the detection antibodies remains a concern, however, and so, Huang said, the company tests its panels for cross-reactivity to determine which assays can and can't be multiplexed together.

"It takes a lot of effort to identify the pairs of antibodies and then to identify the panels of antibodies that can be put together," he said.

Huang declined to specify how far along the company's internal biomarker discovery programs were, noting only that some projects are in the discovery phase, for which the company is using its comprehensive profiling platform, while others are in the verification and validation stages, for which it is using smaller, quantitative array platforms.

Both the hepatocellular carcinoma and ovarian cancer research presented in the PLOS One papers was early stage work. In the former, the researchers examined tumor samples and matching paratumorous tissue samples from 25 hepatocellular carcinoma patients at Sun Yat-sen University.

In the ovarian cancer work, the researchers profiled protein expression levels in 34 ovarian cancer patients and 53 age-matched controls from Sun Yat-sen University, identifying MSP-alpha, TIMP-4, PDGF-R alpha, OPG, and the established ovarian cancer marker CA125 as potential markers for the disease. With this panel, the researchers were able to distinguish between ovarian cancer cases and controls with a specificity of 95 percent and sensitivity of 100 percent. However, these statistics were not generated using a separate validation set, and 25 of the 34 patients in the study had either stage III or IV ovarian cancer, raising questions about the panel's ability to detect early stages of the disease.

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